Probably because you’re using the BuddyPress theme (which of course requires BuddyPress to be active).
Sure, that explains why it breaks after I remove Buddypress, but why the blank white screen when Buddypress is still installed?
I am narrowing the problem down to having too many sites, which is weird.
For example, I deleted about 200 sites and got it working again. So when I have 30 sites assigned to admin everything seems to work fine. But after I add the 200 sites back I begin to see the WSOD as I add new sites from admin.
Anybody have any suggestions?
Might be a memory issue. Anything in your web server error logs?
I found nothing in the error logs to suggest a memory problem, but I went and defined(‘WP_MEMORY_LIMIT’, ‘128M’); and things seem to be stable now.
I have added all the sites back and so far no white screens … which is great news.
Is it OK to leave the MEMORY_LIMIT at 128M? What is the recommended LIMIT for performance on a WPMU install with around 250 sites?
(and thanks for your help)
“Is it OK to leave the MEMORY_LIMIT at 128M? What is the recommended LIMIT for performance on a WPMU install with around 250 sites?”
At least that.
Sounds like this issue’s solved. The extra memory that BuddyPress might use must have just pushed your server over the edge.
Yes, so far so good. I’ll keep it at 128M and see if that holds.
Thanks for the advice.
While we’re talking about the white screen of death, I am making a plugin that works fine if you activate it sitewide and gives the good old white screen when I activate it not sitewide. Any ideas in general why this might happen?
Does any one know exactly what the white screen means, or what specifically causes it?
White screen is always an error of some kind, usually php. that’s why there is no one answer and everyone says read the error logs. 
It;s designed this was to suppress the output of the specific error for security reasons (at least that’s what I remember from a while ago).
